The present invention relates to an aqueous fuel emulsifier package, and more particularly to a method of manufacturing the individual raw materials of a particular emulsifier package to create a superior aqueous fuel emulsion from a source of hydrocarbon fuel, a source of water, and a source of said aqueous fuel emulsifier package.
Recent fuel developments have resulted in a number of aqueous fuel emulsions comprised essentially of a carbon-based fuel, water, and various additives such as lubricants, emulsifiers, surfactants, corrosion inhibitors, cetane improvers, and the like. These aqueous fuel emulsions may play a key role in finding a cost-effective way for internal combustion engines including, but not limited to, compression ignition engines (i.e., diesel engines) to achieve the reduction in emissions below the mandated levels without significant modifications to the engines, fuel systems, or existing fuel delivery infrastructure.
Advantageously, aqueous fuel emulsions tend to reduce or inhibit the formation of nitrogen oxides (NOx) and particulates (i.e., combination of soot and hydrocarbons) by altering the way the fuel is burned in the engine. Specifically, the fuel emulsions are burned at lower temperatures than conventional fuels due to the presence of water. This coupled with the realization that at higher peak combustion temperatures more NOx are typically produced in the engine exhaust, one can readily understand the advantage of using aqueous fuel emulsions.
As is well known in the art, the constituent parts of such aqueous fuel emulsions have a tendency to separate or be unstable over time because of the different densities or relative weights of the primary components. As an example, middle distillate hydrocarbon sources have a density of approximately 0.85 while water sources have a density of approximately 1.0. Because the gravitational driving force for phase separation is more prominent for larger droplets of water, emulsions containing relatively smaller droplets of water will remain stable for longer periods of time. Aqueous fuel emulsion breakdown or phase separation is also influenced by how quickly the water droplets coalescence, flocculate or sediment. The emulsion breakdown is also influenced by the environment in which the aqueous fuel is subjected. For example, high temperatures and dynamic stress can accelerate the deterioration of the aqueous fuel emulsion. Given the high temperatures inherent to combustion devices and the related fuel delivery systems, aqueous fuel emulsions must be designed to withstand a prescribed amount of heat and stress. Any breakdown in the aqueous fuel emulsion can be extremely damaging if not detected before use in combustion. Given the microscopic nature of the suspended particles with the discontinued phase, aqueous fuel emulsions can look good to the naked eye but can actually be considered bad when subjected to quality control standards to one familiar with the art.
Determining the amount of the emulsifier necessary for creating a specific emulsion of a water source and a hydrocarbon source can generally be calculated with calculations common to the art based on material densities, particle sizes of the discontinuous phase, etc. Such measurements are typically summarized in a particle distribution curve of the discontinued phase.
It is commonly recognized that aqueous fuel emulsions can by produced by mixing a liquid hydrocarbon source, an emulsifier source, and a water source. The art of making aqueous fuel emulsions basically relates to three aspects:                1) The specific sequences in which each of the ingredients (or portions thereof) are mixed with the other ingredients (or portions thereof),        2) The specific mechanical mixing procedures of the ingredients, and        3) The specific chemistries of the aqueous fuel emulsifier.        
While a range of different sequences have been recognized, it is generally understood that the principles of aqueous fuel emulsions dictate that the emulsifier supply should be mixed with the external phase of the aqueous fuel emulsion first (or portions thereof) and then with the discontinued phase (or portions thereof) second.
For example, in the case of an oil-phased emulsion the emulsifier supply would be first mixed with the hydrocarbon source before it is mixed with the discontinued phase of water. Conversely, in a water-phased emulsion the emulsifier supply would be first mixed with the water source (or portions thereof) before it is mixed with the discontinued phase of oil (or portions thereof). In the case where portions are premixed, the balance is introduced at a subsequent point as the aqueous fuel emulsion is manufactured.
While there can be several mixing stations during the emulsification process, a high-shear mixing stage is usually required when a water source is mixed with an oil source. Prior to the high-shear mixing, the various stages can be mixed with less intense mixing devices, such as in-line mixers or other common liquid agitators, because the chemicals being mixed have relatively compatible chemical properties. Because of the very different chemical properties of water and oil, significant amounts of mechanical energy are required to reduce the discontinued phase to sizes where they can contribute to a stable aqueous fuel emulsion.
Chemistries for emulsifiers are generally composed of surfactants or soaps, among other things, that comprise a mixture of at least two components: one that is predominantly hydrocarbon soluble and the other that is predominantly water soluble so that the surfactant is balanced such that the interfacial tension between the hydrocarbon and water phases is substantially zero. In other words, each of these chemistries plays a critical role in breaking down the surface tension between the oil and water so a bond can form between the different molecules and to help disperse the water particles (from attracting to each other). This is basically completed through three different types of electrical charged chemistries referred to as cationic (positive charge), anionic (negative charge) and non-ionic (neutral charge), or combinations thereof.
In many cases the emulsifier packages are designed to be soluble in the discontinued phase. The amount of the emulsifier as a percent of the aqueous emulsified fuel will vary based on several factors which include the type and amount of continuous and discontinuous phase, the chemical composition of the emulsifier, and the particle sizes of the discontinued phase. What is needed in the art is a stable emulsifier package.